A three-year program of research is proposed to elucidate the primary biochemical and biophysical causes for cellular injury resulting from the oxidant ozone. The basic hypothesis to be tested is that the primary point of oxidant attack is the cellular plasma membrane and that a loss of critical ions, particularly K ions, alters the metabolism of the cell and destroys cellular homeostasis. Two membrane components, sulfhydryls and unsaturated fatty acids, are highly probable sites of ozone attack and alterations in these molecules would undoubtedly lead to gross changes in permeability and transport properties of the membrane. These studies have utilized two model biological systems. (1) The unicellular alga Chlorella sorokiniana is subjected to ozone under two regions: a) high levels for short durations and b) continuous low levels. K ion levels, specific permeability indicators, level of pertinent enzymes, lipid composition changes, and sulfhydryl alterations have been assayed. (2) Membrane fragments of Red Blood Cells are subjected to ozone to ascertain which biochemicals in the membrane are altered first.